Calling PHP function from JQuery/Ajax

Question

It's clear from reading through threads that I can call a PHP function using Ajax / JQuery, but I can't quite get my head around the particulars.

Let's say I have a function foo() which simply adds 'bar' to some string I pass in. foo() lives in foo.php. To use this in my JavaScript-less HTML, I'd do something like this:

<?php include 'foo.php';?>
<?php echo foo('bar')?>

...and my output is "foobar". Great.

I suspect I do something like so to grab the output of foo() via JavaScript:

<script>
$.post("http://foo.com/foo.php", {
 <Magic happens here> 
}, function(response) {
useTheOutput(response);
});
</script>

....but I'm not clear on whether I should be POSTing or GETing...and how to pass in a value, like 'bar'.

Can anyone push me in the right direction? Here are other threads that discuss the same thing, I just can't connect all the dots:

Call php function from javascript

call function in jquery-ajax

• Sgoettschkes: You seem to lack the understanding of what php is, how it differs from javascript and what ajax does. I recommend using a tutorial which covers this stuff.
• MetalFrog: There is nothing 'magic' about web development. It is a series of requests and responses.
• Russell Christopher: Actually, I get it. I have a php function which generates a "ticket". This function must be fired server-side as the request itself needs to come from a trusted IP address, which is the server on which the .php page lives. I need to call this function from JavaScript - I see other people have accomplished this on StackOverFlow, but I still need a little help.
• ohaal: For your POST/GET question, use POST for destructive actions such as deletion, editing, and creation. Reason for this is because you can't hit a POST action in the address bar of your browser. Use GET when it's safe to allow a person to call an action from the address bar, i.e. guiding you to a specific page, setting options in a form etc.

Answer 1

Solution:

PHP (foo.php):

<?php
function generateTicket()
{
 //get_trusted_ticket_direct is another function that does heavy lifting...
 $ticket= get_trusted_ticket_direct($_POST['server'], $_POST['user'], $_POST['targetsite']);
 echo $ticket;
}
if ($_POST['toDo'] == 'generateTicket') {
 generateTicket();
}
?>

JavaScript:

$(document).ready(function() {
 // Handler for .ready() called.
 $.post('http://foo.com/foo.php', {
 toDo: 'generateTicket',
 server: 'serverName',
 user: 'userName',
 targetsite: '' 
 }, function(response) {
 alert(response);
 });
});​